Adaptation of Listeria monocytogenes in a simulated cheese medium: effects on virulence using the Galleria mellonella infection model. (25th March 2013)

• Record Type: Journal Article
• Authors: Schrama, D.; Helliwell, N.; Neto, L.; Faleiro, M.L.
• Is Part Of: Letters in applied microbiology. Volume 56:Number 6(2013:Jun.)
• Page Start: 421
• Page End: 427
• Publication Date: 2013-03-25
• Subjects: Microbiology -- Periodicals; 660.62
• DOI: 10.1111/lam.12064
• Languages: English
• ISSNs: 0266-8254

Abstract

<abstract abstract-type="main" xml:lang="en" id="lam12064-abs-0001"> <title>Abstract</title> <sec id="lam12064-sec-0101" sec-type="section"> <p>The aim of this study was to evaluate the effect of the acid and salt adaptation in a cheese‐based medium on the virulence potential of <italic>Listeria monocytogenes</italic> strains isolated from cheese and dairy processing environment using the <italic>Galleria mellonella</italic> model. Four <italic>L. monocytogenes</italic> strains were exposed to a cheese‐based medium in conditions of induction of an acid tolerance response and osmotolerance response (pH 5·5 and 3·5% w/v NaCl) and injected in <italic>G. mellonella</italic> insects. The survival of insects and the <italic>L. monocytogenes</italic> growth kinetics in insects were evaluated. The gene expression of <italic>hly</italic>, <italic>actA</italic> and <italic>inlA</italic> genes was determined by real‐time PCR. The adapted cells of two dairy strains showed reduced insect mortality (<italic>P</italic> < 0·05) in comparison with nonadapted cells. <italic>Listeria monocytogenes</italic> Scott A was the least virulent, whereas the cheese isolate C882 caused the highest insect mortality, and no differences (<italic>P</italic> > 0·05) was found between adapted and nonadapted cells. The gene expression results evidenced an overexpression of virulence genes in cheese‐based medium, but not in simulated insect‐induced conditions. Our results suggest that adaptation to low pH and salt in a cheese‐based medium can affect the virulence of <italic>L. monocytogenes, </italic> but this effect is strain dependent.</p> </sec> <sec id="lam12064-sec-0102" sec-type="section"> <title>Significance and Impact of the Study</title> <p>In this study, the impact of adaptation to low pH and salt in a cheese‐based medium on <italic>L. monocytogenes</italic> virulence was tested using the Wax Moth <italic>G. mellonella</italic> model. This model allowed the differentiation of the virulence potential between the <italic>L. monocytogenes</italic> strains. The effect of adaptation on virulence is strain dependent. The <italic>G</italic>. <italic>mellonella</italic> model revealed to be a prompt method to test food‐related factors on <italic>L. monocytogenes</italic> virulence.</p> </sec> </abstract>